This invention relates generally to remote object identification and speed determination, and more particularly concerns a system including a novel label on an object as well as novel apparatus and techniques for automatically reading the label at one or more distances. The invention has particular application to the problem of automatically identifying vehicles carrying such labels as well as checking the speeds of such vehicles.
Remote identification systems for vehicles or other objects have been in existence for some years. These systems are often complex and costly devices in which rapid, reliable readings are often not achieved. Some such systems use a television camera to produce an image of a viewing area which includes the license plate on a vehicle. This image is then analyzed to locate the license plate and finally character recognition techniques are used to read the alphanumeric characters on the license plate. Such systems are understandably complex and require expensive equipment to carry out the tasks of first locating the license plate and then reliably and rapidly identifying the moving vehicles. Furthermore, these systems are easily affected by poor lighting conditions. In some systems the license numbers are actually read by human operators after the vehicle license plates have been automatically located and photographed. Of course the use of operators makes the operation even more expensive and time consuming.
Radar devices are often used to measure the speeds of moving vehicles but radar does not attempt to identify an individual vehicle and uncertainty in determining which vehicle is actually being timed can cause costly and time consuming mistakes. According to the present invention the vehicle being timed can be positively identified and confusion between vehicles can be avoided.
A prime object of the invention is to provide apparatus for continuously scanning across a limited area at a predetermined distance into which a bar code label carried by an object or vehicle may move and, in a single scan across the bar code, the apparatus will check to ensure that the total length of the bar code information is detected and also read the information when such a detection is made. Furthermore, the label can be detected if it is located anywhere in the scanned area at the predetermined distance.
It is a further object of the present invention to create a novel label as well as simple and reliable apparatus and techniques for reading such labels from a head-on or other positions by detecting radiation from such labels in daylight or at night.
Another object of the invention is to have the label invisible and transparent so that it can be placed on or in a vehicle windshield and be large enough to be reliably read from a head-on position by an automatic remote reader using only ambient radiant energy and yet, because it is invisible, not obscure the view of the vehicle driver.
Another aspect of the invention is to have a label which is transparent and reflects or emits only invisible radiation so that the label can be placed in the normal line of vision of the driver while driving. Thus the label cannot be covered without also hindering the driving visibility of the driver or making the vehicle easily distinguishable.
Still another aspect of the invention is the use of a bar code label which can be automatically checked for completeness and read on a single line scan across the label.
A further object of this invention is to provide apparatus which positively detects a moving vehicle at least two precisely determined locations so that the speed of the vehicle can be determined by utilizing the lapse of time between the arrival of the vehicle at each of the at least two predetermined locations.
Further objects and advantages of the invention will become apparent from a consideration of the drawings and the following detailed description.